The prior art, as exemplified in U.S. Pat. Nos. 2,919,482, 3,015,868, 3,197,537, 3,199,162, and 3,908,242, contains a number of slide fasteners having continuous filaments formed into coils or meander patterns to form interlocking coupling elements wherein heel portions of the filament convolutions contain notches or flattened segments. These notches or flattened portions are formed by crimping rollers deforming the filament cross section during the formation of the filament into the desired coil or meander configuration. These notches or flattened heels are utilized to retain attaching threads or to form slider flange engaging surfaces.